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Observed decline of the Atlantic meridional overturning circulation 2004–2012

Observed decline of the Atlantic meridional overturning circulation 2004–2012
Observed decline of the Atlantic meridional overturning circulation 2004–2012
The Atlantic meridional overturning circulation (AMOC) has been observed continuously at 26° N since April 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable-based measurements of the Gulf Stream and satellite derived Ekman transport. The time series has recently been extended to October 2012 and the results show a downward trend since 2004. From April 2008 to March 2012, the AMOC was an average of 2.7 Sv (1 Sv = 106 m3 s?1) weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the southward flow above the thermocline. The increased southward flow of warm waters is balanced by a decrease in the southward flow of lower North Atlantic deep water below 3000 m. The transport of lower North Atlantic deep water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).
1812-0792
29-38
Smeed, D.A.
79eece5a-c870-47f9-bba0-0a4ef0369490
McCarthy, G.
99241bcb-5667-469d-b7ae-4d308d516bd6
Cunningham, S.A.
07f1bd78-d92f-478b-a016-b92f530142c3
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Rayner, D.
60eaf35c-c54e-447b-8551-efc08637d122
Johns, W.E.
e69b0088-c832-4ed8-94f6-9c5e9e6f62af
Meinen, C.S.
e1d8f782-ccdf-4f81-98c4-cc1c7701165c
Baringer, M.O.
b8dab4b9-918b-4bc9-a033-dcbeb03f5730
Moat, B.I.
497dbb18-a98f-466b-b459-aa2c872ad2dc
Duchez, A.
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Bryden, H.L.
7f823946-34e8-48a3-8bd4-a72d2d749184
Smeed, D.A.
79eece5a-c870-47f9-bba0-0a4ef0369490
McCarthy, G.
99241bcb-5667-469d-b7ae-4d308d516bd6
Cunningham, S.A.
07f1bd78-d92f-478b-a016-b92f530142c3
Frajka-Williams, E.
da86044e-0f68-4cc9-8f60-7fdbc4dc19cb
Rayner, D.
60eaf35c-c54e-447b-8551-efc08637d122
Johns, W.E.
e69b0088-c832-4ed8-94f6-9c5e9e6f62af
Meinen, C.S.
e1d8f782-ccdf-4f81-98c4-cc1c7701165c
Baringer, M.O.
b8dab4b9-918b-4bc9-a033-dcbeb03f5730
Moat, B.I.
497dbb18-a98f-466b-b459-aa2c872ad2dc
Duchez, A.
d73f2e60-bc41-4fb5-9686-6e12048a6f2d
Bryden, H.L.
7f823946-34e8-48a3-8bd4-a72d2d749184

Smeed, D.A., McCarthy, G., Cunningham, S.A., Frajka-Williams, E., Rayner, D., Johns, W.E., Meinen, C.S., Baringer, M.O., Moat, B.I., Duchez, A. and Bryden, H.L. (2014) Observed decline of the Atlantic meridional overturning circulation 2004–2012. Ocean Science, 10 (1), 29-38. (doi:10.5194/os-10-29-2014).

Record type: Article

Abstract

The Atlantic meridional overturning circulation (AMOC) has been observed continuously at 26° N since April 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable-based measurements of the Gulf Stream and satellite derived Ekman transport. The time series has recently been extended to October 2012 and the results show a downward trend since 2004. From April 2008 to March 2012, the AMOC was an average of 2.7 Sv (1 Sv = 106 m3 s?1) weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the southward flow above the thermocline. The increased southward flow of warm waters is balanced by a decrease in the southward flow of lower North Atlantic deep water below 3000 m. The transport of lower North Atlantic deep water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).

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e-pub ahead of print date: 13 September 2013
Published date: 6 February 2014
Organisations: Physical Oceanography, Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 356498
URI: http://eprints.soton.ac.uk/id/eprint/356498
ISSN: 1812-0792
PURE UUID: 5593349b-e830-4970-bcbf-1a2ec9fcdfa9
ORCID for E. Frajka-Williams: ORCID iD orcid.org/0000-0001-8773-7838
ORCID for H.L. Bryden: ORCID iD orcid.org/0000-0002-8216-6359

Catalogue record

Date deposited: 05 Sep 2013 09:33
Last modified: 26 Nov 2019 01:59

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